The present invention relates to an anti-collision system for vehicles. The invention is especially useful for passenger cars, taxis, trucks and buses, and is therefore described below particularly with respect to such vehicles, but the invention, or some aspects of the invention, could also advantageously be used for other types of vehicles, e.g., trains and aircraft.
One of the most frequent causes of vehicle accidents is the failure of a vehicle to maintain an assured safe distance behind another vehicle to prevent a rear end collision should the front vehicle suddenly stop. The assured safe distance required to prevent such a rear-end collision depends on the reaction time of the vehicle driver before the brake pedal is actually depressed, and the braking distance traversed by the vehicle before it comes to a complete stop after the braking pedal has been depressed. Both of these factors vary according to the surrounding circumstances at the time of driving.
In order to prevent collisions, many parameters, which are constantly changing during the year or even during a trip, may affect the stopping distance of the vehicle and therefore should be taken into account. These parameters include: the condition of the driver, such as the driver's reaction time; the condition of the vehicle, such as the vehicle load, the tires pressure; and environmental conditions, such as road type, visibility, skidding condition.
It is very important that the computer determines the danger-of-collision distance according to the specific conditions existing at the time the vehicle is being operated. Thus, if the determined danger-of-collision distance is too high for the specific operating conditions, there will be a high rate of "false alarms"; this will reduce the credibility of the system to the driver, which can result in a true collision condition being ignored. 0n the other hand, if the determined danger-of-collision distance is too low for the specific operating conditions, this could result in failure to actuate the alarm in time when there was truly a collision condition.
Many anti-collision systems have been proposed, but insofar as I am aware, none has yet gained any widespread use, probably because the proposed systems have not taken into consideration the variable nature of the many parameters which influence the reaction time and/or the braking distance involved at any particular time for determining the assured safe distance required to be maintained.
An object of the present invention is to provide an anti-collision system which is more closely responsive to the actual driving conditions for actuating an alarm.